Equipped with 1 SLD (Special Low Dispersion) glass element for maximum image quality, the new Sigma Global Vision teleconverters utilize a splash and dust proof construction for long lasting durability. Created exclusively for the Global Vision lenses, these teleconverters ensure the utmost in compatibility, even for large diameter lenses. With effective AF at F8 and 1.4x the reach, get the most out of your Sigma lens.